I’m not from the area but does anyone actually fly from SEA to PDX assuming they have a car? It’s not like SeaTac is even that close to Seattle. And depending on where you live and destination plans it’s hard for me to imagine trading a less than 3 hour drive for a train trip.
From the number of flights offered, I think it’s much more common than you might think. My guess is that part of the reason has to to with Seattle’s very very bad traffic. I once spent 4 hours traveling less than 15 miles on a drive heading south from the city center, and I don’t think that’s even super anomalous.
I can't relate to this at all. I would trade driving for a train trip if the total duration is somewhat comparable (or even a little bit longer), especially if I would have to make the trip regularly.
I don't think flying is convenient but taking a HSR-train is.
It depends on a lot of factors. Where do you live relative to the train station? How annoying is the drive? Do you want/need a car on the other end? New York checks two of those boxes for me. (Getting to the train is out of the way.) But a lot of places that could be train trips I’d want a car once I got there.